A number of mathematical and computer models are currently available to calculate initial dilution of treated wastewater effluent discharges into the ocean. This paper presents a comparative evaluation of six initial dilution models using data from Boston Metropolitan District Commission's proposed ocean discharge. To determine the reliability of application of these models, field data and results of dye studies conducted for the Alyeska Marine Terminal outfall in Port Valdez, Alaska were used to check against calculated dilutions from these models. It was found that some of the models provided dependable results.